SKU: 27685105773

A-Star 32U4 Micro Pololu 3101

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Description

A-Star 32U4 Micro Pololu 3101The A Star 32U4 Micro is a tiny programmable module featuring the ATmega32U4 AVR microcontroller. It packs a Micro USB interface and 18 digital input output pins (of which 7 can be used as PWM outputs and 8 as analog inputs) onto a board measuring only 1 0. 6 and ships preloaded with an Arduino compatible bootloader. A Star 32U4 Micro, bottom view with U. S. quarter for size reference. Overview The Pololu A Star 32U4 Micro is a general purpose

The A-Star 32U4 Micro is a tiny programmable module featuring the ATmega32U4 AVR microcontroller. It packs a Micro-USB interface and 18 digital input/output pins (of which 7 can be used as PWM outputs and 8 as analog inputs) onto a board measuring only 1″ × 0.6″ and ships preloaded with an Arduino-compatible bootloader.


 

A-Star 32U4 Micro, bottom view with U.S. quarter for size reference.

Overview

The Pololu A-Star 32U4 Micro is a general-purpose programmable module based on the ATmega32U4 AVR microcontroller from Microchip (formerly Atmel), which has 32 KB of flash program memory, 2.5 KB of RAM, and built-in USB functionality. Onboard features of the A-Star (abbreviated A*) include a 16 MHz resonator, a USB Micro-B connector, an in-system programming (ISP) header, and a pair of indicator LEDs. A voltage regulator and power selection circuit allow the board to be powered from either USB or an external 5.5 V to 15 V source, while a resettable PTC fuse on the USB VBUS supply and reverse protection on VIN help protect it from accidental damage.

The A-Star 32U4 Micro breaks out 15 general-purpose I/O lines along two rows of pins, including 7 usable as PWM outputs and 8 usable as analog inputs; another three GPIO pins can be accessed through the 6-pin ISP header. It fits all this into a 20-pin dual in-line package (DIP) measuring only 1″ × 0.6″ (even smaller than competing ATmega32U4 boards like the Teensy 2.0 and Pro Micro), and its 0.1″ pin spacing makes the A* easy to use with solderless breadboards, perfboards, and 0.1″-pitch connectors.

Our comprehensive user’s guide provides the basics you need to get started with the A-Star as well as detailed technical information for advanced users.

This product requires a USB A to Micro-B cable (not included) to connect to a computer.

Features

  • Dimensions: 1″ × 0.6″ (1.05″ × 0.6″ including USB Micro-B connector)
  • Programmable 16 MHz ATmega32U4 AVR microcontroller
    • 32 KB flash (4 KB used by bootloader, leaving 28 KB available for user program by default)
    • 2.5 KB SRAM
    • 1 KB EEPROM
    • Native full-speed USB (12 Mbps)
  • Preloaded with Arduino-compatible bootloader (no external programmer required)
  • Many I/O lines in a small package
    • 15 general-purpose I/O pins available along the sides of the board
    • 3 additional I/O pins available on ISP header
    • 7 pins can be configured as hardware PWM outputs
    • 8 pins can be configured as analog inputs
  • 2 user-controllable LEDs
  • Can be powered from USB or external 5.5 V to 15 V source on VIN
  • PTC fuse on VBUS supply
  • Reverse-voltage protection on VIN supply
  • 6-pin ISP header for use with an external programmer
  • Comprehensive user’s guide

Arduino compatibility

The A-Star 32U4 ships with a preloaded Arduino-compatible bootloader (which uses 4 KB of flash memory, leaving 28 KB available for the user program). We provide a software add-on that enables the board to be easily programmed from the Arduino environment.

The A-Star 32U4 uses the same microcontroller as the Arduino Leonardo and Arduino Micro and runs at the same frequency, making it just as powerful. Although the larger boards offer a few more I/O pins, the A-Star 32U4 Micro fits in an area half that of the Arduino Micro, and it takes up only 11% as much area as a standard full-size Arduino!

 

Pololu A-Star 32U4 Micro, Pololu A-Star 32U4 Mini SV, Arduino Micro, and Arduino Leonardo.

Pinout

 

This diagram identifies the I/O and power pins on the A-Star 32U4 Micro; it is also available as a printable PDF (409k pdf). For more information about the ATmega32U4 microcontroller on this board, see Microchip’s ATmega32U4 documentation.

Printed on the A* circuit board are indicators that you can use to quickly identify each pin’s capabilities: a triangle next to the pin means it can be used as an analog input, and a square wave symbol under the pin number means it can be used as a PWM output.

The board can either be powered directly from the USB 5 V supply or from a separate 5.5 V to 15 V source on the VIN pin, which is reduced to 5 V by a 100 mA low-dropout (LDO) regulator; you can access this 5 V supply through the 5V power output pin. Additionally, the ATmega32U4 contains an internal 3.3 V regulator whose output is available on the 3V3 pin. Current drawn from the 3V3 output should not exceed about 50 mA, and when the board is being powered through VIN, the sum of the 5V output current, 3V3 output current, GPIO output current, and current used by the board itself (typically about 25 mA) should not exceed 100 mA.

Included hardware

A 1×20-pin breakaway 0.1″ male header is included with the A-Star 32U4 Micro, which can be soldered in to use the board with perfboards, breadboards, or 0.1″ female connectors. (The headers might ship already separated into two 1×10 pieces.) Also included is a 2×3 header that can be installed to allow external programming of the microcontroller through the AVR ISP interface, such as with our USB AVR programmer.

A-Star 32U4 Micro with included optional headers.

A-Star 32U4 Micro with soldered headers and connected USB cable.

The A-Star family

 

From top to bottom: A-Star 328PB Micro, 32U4 Micro, 32U4 Mini SV, and 32U4 Prime SV.

The A-Star 32U4 Micro is a part of our larger A-Star family, all of whose members are based on AVR microcontrollers and are preloaded with Arduino-compatible bootloaders. The table below shows some key features and specifications of our A-Star microcontroller boards to help you choose the right one for your application.







A-Star 328PB Micro A-Star 32U4 Micro A-Star 32U4 Mini ULV

A-Star 32U4 Mini LV

A-Star 32U4 Mini SV
A-Star 32U4 Prime LV

A-Star 32U4 Prime SV
A-Star 32U4 Robot Controller LV

A-Star 32U4 Robot Controller SV
Microcontroller: ATmega328PB ATmega32U4
User I/O lines: 24 18 26 26(1) 26(1)
PWM outputs: 9 7 7 7 7(1)
Analog inputs: 8 8 12 12 12(1)
Ground access points: 6 2 4 43 44
User LEDs: 1 2 3 3 3
User pushbuttons: 3 3
USB interface: Yes Yes Yes Yes
Reset button: Yes   Yes Yes Yes
Power switch:     Yes Yes
Buzzer option:     Yes Yes
microSD option:     Yes  
LCD option:     Yes  
Motor drivers:       Yes
Operating voltage: 3.3V VCC: 3.8 V to 15 V
5V VCC: 5.5 V to 15 V
5.5 V to 15 V ULV: 0.5 V to 5.5 V
LV: 2.7 V to 11.8 V
SV: 5 V to 40 V
LV: 2 V to 16 V
SV: 5 V to 36 V
LV: 2.7 V to 11 V
SV: 5.5 V to 36 V
Regulator type: 3.3 V or 5 V linear 5 V linear 5 V switching

ULV: step-up
LV: step-up/step-down
SV: step-down
5 V switching

LV: step-up/step-down
SV: step-down
5 V switching

LV: step-up/step-down
SV: step-down
Regulated current:(2) 100 mA 100 mA ULV: 500 mA
LV: 1 A
SV: 800 mA
LV: 1.8 A
SV: 1 A
LV: 1 A
SV: 1.5 A
Dimensions: 1.3″ × 0.7″ 1″ × 0.6″ 1.9″ × 0.7″ 2.8″ × 2.1″ 2.6″ × 2.2″
Weight: 1.5 g(3) 1.3 g(3) 3.4 g(3) 13 g to 33 g 14 g to 23 g
1 Some microcontroller resources are used by on-board hardware.
2 These values are rough approximations for comparison purposes. Available current depends on input voltage, current consumed by the board, ambient conditions, and regulator topology. See product documentation and performance graphs for details.
3 Without included optional headers.

Specifications

Parameter Value
Size 0.6″ × 1.05″ × 0.18″
Weight 1.3 g
Processor ATmega32U4 @ 16 MHz
Ram size 2560 bytes
Program memory size 32 Kbytes
Motor channels 0
User i/o lines 18
Minimum operating voltage 5.5 V
Maximum operating voltage 15 V
Logic voltage 5 V
Reverse voltage protection? Y
External programmer required? N
PCB dev codes ac01a
Other PCB markings 0J8063

Resources

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Exchange/Return Notes
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SKU: 27685105773

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Amazon Customer
Cuba, US
★★★★★ 5
My Dog Went Crazy Over This Electric Octopus Toy!
Color: Blue
I was worried sick my fur kid would be super bored home alone while I work, so when I stumbled on this electric octopus toy, I grabbed it right away—and it’s way better than I expected! Let’s start with the quality: the plush fabric feels soft and squishy but so sturdy. It’s not the cheap kind that sheds fur if you tug it, and the stitches are nice and neat. My dog loves chewing on toys, and he’s been playing with this for almost two weeks now—no pilling, no fraying. The durability’s seriously on point. Using it is totally hassle-free, too. It was already charged right out of the box—I just pressed the little button on the side, and it started moving. It has two modes: slow mode makes the octopus wiggle gently, like it’s crawling slowly. Fast mode? It wiggles and scurries around, and the speed’s perfect—my dog can keep up but still has to work a little. When he first saw it, he circled it three times, sniffed it, then backed up right away. He stared at it all cautious, even hid under the couch to spy on it for a bit. That little look was so funny and cute, I couldn’t stop laughing. Now they’re total best buds! Every morning, as soon as I turn the toy on, he runs over with his little bed in his mouth and plops down next to it, waiting for it to move. Sometimes the octopus crawls under the table, and he’ll paw at it for ages. If he can’t reach it, he’ll look up and bark at me like, “Hey, help me get it!” Watching him chase it around, jumping to pounce—his tail wags like a little flag the whole time. It makes the house feel so much livelier, and I don’t have to stress about him being lonely when he’s home alone anymore. Quick tips for all you fellow pet parents: First, the toy makes a tiny motor hum when it moves. It’s not loud, but if your dog’s super skittish or scared of small noises, give him a few days to get used to it. Second, always keep an eye on him while he plays. Mine tried to bite off one of the octopus’s tentacles once—I stopped him just in time. The toy has a motor inside, so you gotta make sure he doesn’t swallow any small parts. Oh, and the plush cover zips off! If it gets dirty, just throw it in warm water, wash it, and once it’s dry, it looks good as new. Super easy to clean. Overall, this electric octopus toy’s the best pet buy I’ve made lately. Great quality, no hassle to use, and it keeps my dog entertained for hours. Every time I see my fur kid’s happy little face while he plays, I think, “Man, this was totally worth the money.” Def recommend it to anyone who wants a fun little buddy for their dog!
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Reviewed in the United States on August 26, 2025
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Amazon Customer
Grantham, US
★★★★★ 5
Good quality and safe for my pet! Lots of fun to play with!
Color: Blue
Worth buying for your pet! My American Bulldog wouldn’t leave it alone !
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Reviewed in the United States on June 11, 2026
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Karyn Bennett
Pawtucket, US
★★★★★ 4
Super fun but fabric not durable for rough play.
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My dog absolutely love this, but the octopus cloth fell apart within the first day. He doesn’t usually play rough with his toys, but he was able to shred this octopus fabric very easily. He was very passionate in his playfulness and he’s a big dog, but he was able to put massive holes in the fabric within the first hour of play. The Ball still works, however so hopefully we can find another toy to stick it in.
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Brady Perry
Bozeman, US
★★★★★ 5
My dog's favorite toy to date
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Heavy duty material that my dog has not destroyed. The vibrating ball inside is made of hard plastic, so beware if your dog likes to shake their toys, it definitely hurts to get whacked by this. The velcro keeping the ball inside is also heavy duty and takes a lot of strength to open. All in all, its a great toy and one of my dog's favorites.
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MandyMT
Draper, US
★★★★★ 3
Good enough.
Color: Blue
A little smaller than I thought and the battery doesn't last too long. But my puppy enjoys it enough. It is holding up well to her teeth as well.
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Reviewed in the United States on April 16, 2026

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